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authorSzabolcs Nagy <nsz@port70.net>2013-08-15 10:14:46 +0000
committerSzabolcs Nagy <nsz@port70.net>2013-08-15 10:14:46 +0000
commitc599f4f4d705ba215a2672b92baa1c29d9dd0735 (patch)
treef9931ee00f59bae9aba69b9dbcff18a5c1613018 /src/math/asin.c
parentcd18dc8525a275323819ac4c7826cc3404202f7b (diff)
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math: fix asin, atan, log1p, tanh to raise underflow on subnormal
for these functions f(x)=x for small inputs, because f(0)=0 and f'(0)=1, but for subnormal values they should raise the underflow flag (required by annex F), if they are approximated by a polynomial around 0 then spurious underflow should be avoided (not required by annex F) all these functions should raise inexact flag for small x if x!=0, but it's not required by the standard and it does not seem a worthy goal, so support for it is removed in some cases. raising underflow: - x*x may not raise underflow for subnormal x if FLT_EVAL_METHOD!=0 - x*x may raise spurious underflow for normal x if FLT_EVAL_METHOD==0 - in case of double subnormal x, store x as float - in case of float subnormal x, store x*x as float
Diffstat (limited to 'src/math/asin.c')
-rw-r--r--src/math/asin.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/src/math/asin.c b/src/math/asin.c
index 3e8f99ed..c926b188 100644
--- a/src/math/asin.c
+++ b/src/math/asin.c
@@ -82,11 +82,9 @@ double asin(double x)
}
/* |x| < 0.5 */
if (ix < 0x3fe00000) {
- if (ix < 0x3e500000) {
- /* |x|<0x1p-26, return x with inexact if x!=0*/
- FORCE_EVAL(x + 0x1p120f);
+ /* if 0x1p-1022 <= |x| < 0x1p-26, avoid raising underflow */
+ if (ix < 0x3e500000 && ix >= 0x00100000)
return x;
- }
return x + x*R(x*x);
}
/* 1 > |x| >= 0.5 */